We look at the pros and cons of rail and rail-less PV mounting systems

Should you go with a rail or rail-less PV mounting system on your next installation? Depending on who you ask, you will get strong opinions for both. I liken the choice to dieting. Don’t eat meat! Actually, don’t eat carbs! No, it’s sugar that’s the killer! Milk is bad! You need milk!

The commonality here, at least to me, is everyone is right, and no one is right. What works for one person or project may not work for another, and maybe the answer is a little bit of all of the above. The real key is knowing what you need, what you prefer and the attributes of your available choices.

All systems have their pluses and minuses, and depending on the job at hand or your business plan, either could be the right solution for you and your customers. So, when, where and why would you go in one direction or another?

Reasons for Rails

For starters, it is easier to start. Rails involve a lower learning curve. You can get a crew trained on system installation fairly quick, and part of the reason for this is a more forgiving layout. SunModo, which offers all types of systems, says that on a straight-forward roof, your layout time is reduced.

The most ideal applications, according to Jason Xie, president at Magerack, is a large, simple array layout or a crooked roof. “A roof with a lot of obstacles — vents, stack, etc. — can present issues,” Xie says.

Look for low to moderately pitched roof applications in the 8 to 44 degrees range. Railed systems will require more engineering on steep slope pitched roof applications, 45 degrees or greater, according to SunModo.

“All rackless systems don’t use rails. That’s a time savings, but if the number of attachments is higher, if the parts costs are higher, or if there are still fiddly little parts that need adjustment, the overall costs are higher — not lower,” says Barry Cinnamon, founder of Spice Solar. “Installers should carefully account for all parts, including roof attachments.”

Some of the benefits aren’t inherent in the general rail system, but have been built in to select products. PV Racking, for example, has eliminated the need for clamps on the roof, which increases the speed of installation and save 20 to 30 percent in labor time. Its elongated L-Foot allows for faster and easier rail alignment too.

Reasons to Share

Shared rail solutions use rail to hold the modules in place, but reduce components elsewhere, such as mid and end clamps. As Shane Shamoo, president of Solar Speedrack, explains it, shared rail systems cover the entire side of the module, and the module frame becomes “bonded” to the rails and reduces the strain on the module.

“Because the rails are shared, a two-up installation would require only three rails as compared to four for a standard mid and end clamp system,” he says. This provides its own unique nimbleness for either landscape or portrait installations on all roof types. Shared rail also requires fewer roof penetrations, lessening the potential of a “floating” penetration.

SunModo says shared rail is great when modules are in landscape and the rail has to be run E-W and you cannot clamp to the short sides of the module, or when the rail has to be run N-S and the module must be in portrait. Less than ideal shared rail applications would be those with sagging trusses, uneven shingles, uneven roof framing or any other situation that would cause difficulty creating perfectly level rows of rail.

“Since we offer a shared rail system that does not require clamps, the first rail automatically aligns the first row of panels, which eliminates the need to straighten panels and speeds up the installation,” says Devin Paris of PV Racking’s shared rail system. Some systems come with rail spacers to allow for fast and easy spacing between the rails, eliminating the need to pull a measurement between each rail.

Reasons for Rail-less

As you might expect, the benefits of a rail-less solution come from not having rails. I know, I really blew the cover off that one, but it’s worth understanding those benefits: Rail-less products are compact, easy to handle and cheaper to ship.

“A rail-less system provides the suppliers the opportunity to cut manufacturing and shipping costs, and the installers are limiting time on the roof with fewer components to handle and install,” SunModo noted.
Milton Nogueira, business development manager with Roof Tech, notes that it is easier to handle any increments of PV modules, which also opens up more possibilities such as any pitched roof top with asphalt roofing, roofs with less space or roofs with lots of obstacles.

Rail-less mounting can be much quicker, but installers must know what they are doing as there can be a steeper learning curve.

Rail-less is also good for mounting in landscape, but less ideal for portrait orientation, says SunModo. Xie recommends avoiding rail-less on crooked roofs, higher wind areas and tile roofs. Nogueira says he would avoid discrepant roof surfaces with variations over 1 in. You’ll always want to consider the extra attachment points you are adding — the more attachment points, the lower the point load and the less impact on the attachment due to thermal contraction and expansion.

System Profiles: Residential Rooftop

SunModo Sundock Rail-free anchor system

The SUNDOCK Rail-free system offers universal end and mid clamps, which reduce inventory, and allows for snapping in the downslope panel edge as installers work their way up the roof. This means no more reaching over modules to tighten the mid clamps. Finally, the system offers post-module assembly leveling for height adjustments after the modules are installed.

Material: Aluminum and stainless steel

Flashing included? Yes

Certifications: UL 2703 (Pending)

Warranty: 20-year

Roof Tech’s E Mount AIR (Gen II)

The E Mount AIR Gen II, has improved features from its predecessor such as IBC 2015 and IRC 2015 compliance, increased warranty terms, fewer parts count, preassembled clamp kit, higher level of adjustability, PE stamped letters and an integrated flashing system. They are fastened with wood screws for direct deck attachment. Roof Tech systems are 100 percent weatherproof certified by the International Code Council Evaluation Services for durability and water resistance and can be installed in about half the time when compared to a conventional lag/rail system, according to the company.

Material: Anodized aluminum

Flashing included? Yes

Certifications: UL 2703, ASTM 2140, ICC ESR-3575

Warranty: 20-year

PV Racking’s PV Stealth

PV Stealth is designed with ease and flexibility in mind. Its “clamp-free” design allows for a faster installation of panels, fewer parts and vertical and horizontal adjustability. The big pitch from PV Racking is to remove clamps from the equation and simply lay your panels into place.

Material: 6000 series aluminum

Flashing included? Optional

Certifications: CSA UL 2703

Warranty: 15-year

Everest’s CrossRail Shared Rail System

CrossRail Shared Rail uses fewer rail resulting in fewer roof attachments. This means you can save money on labor, material and reduce time on the roof. To simplify installation, its Slider Kit provides North-South adjustability for easy module alignment. In addition, its structural Rail Connectors allows for safe and quick preassembly of rails on the ground. As an integrated grounding system, CrossRail Shared Rail only requires one lug per sub-array.

Material: Aluminum, stainlesssteel hardware

Flashing included? With EverFlash Kits

Certifications: UL listed

Warranty: 12-year

Solar Speedrack’s HRS160 Hybrid Racking System

The HRS160 Hybrid Racking design allows the installer to mount the rails in standard or shared rail configurations. This paired with its Solar SpeedFoot, a non-penetrating solar roof mount, yields increased savings on solar installations. The Solar SpeedRack focus is fewer roof penetrations and reduced components for faster install times.

Material: Various materials

Flashing included? Optional

Certifications: UL 2703, UL 1703, PE Certified

Warranty: 20-year limited

MageMount Rail-less Solar Mounting System

This system has separate components for module connections and roof attachments. The roof attachment solutions cover all roof types including composition shingle roof, tile roof, stone-coated steel tile roof, etc. All mounting components, including roof attachments, are self-bonded and grounded with one grounding lug. The system is flexible, making it easy to adjust the roof attachments’ lateral position and module height.